Abstract
As the received radar signal is the sum of signal contributions overlaid in one single pixel regardless of the travel path, the multipath effect should be seriously tackled as the multiple bounce returns are added to direct scatter echoes which leads to ghost scatters. Most of the existing solution towards the multipath is to recover the signal propagation path. To facilitate the signal propagation simulation process, plenty of aspects such as sensor parameters, the geometry of the objects (shape, location, orientation, mutual position between adjacent buildings) and the physical parameters of the surface (roughness, correlation length, permittivity)which determine the strength of radar signal backscattered to the SAR sensor should be given in previous. However, it's not practical to obtain the highly detailed object model in unfamiliar area by field survey as it's a laborious work and time-consuming. In this paper, SAR imaging simulation based on RaySAR is conducted at first aiming at basic understanding of multipath effects and for further comparison. Besides of the pre-imaging simulation, the product of the after-imaging, which refers to radar images is also taken into consideration. Both Cosmo-SkyMed ascending and descending SAR images of Lupu Bridge in Shanghai are used for the experiment. As a result, the reflectivity map and signal distribution map of different bounce level are simulated and validated by 3D real model. The statistic indexes such as the phase stability, mean amplitude, amplitude dispersion, coherence and mean-sigma ratio in case of layover are analyzed with combination of the RaySAR output.
Highlights
Multipath propagation is a tricky problem in SAR imaging processing
This paper aims at analyzing those pixels contaminated by the multipath propagation and distinguishing different bounce level
In the Lupu Bridge case, SAR image simulation method based on RaySAR has been used for multipath analysis at first
Summary
Few research on multipath have been done Those pixels corresponding to the multipath incorporate false travel path leading to ghost scatters(Auer et al, 2011). To recover the true signal travel path, namely, signal transmission from the sensor, interaction with illuminating objects on earth surface, sum of backscattering energy at receiver, several SAR image simulation approaches, such as RaySAR(Auer, 2011), CohRaS(Hammer and Schulz, 2009), and SARViz(Balz and Stilla, 2009), can be employed to reveal the relationship between signatures in SAR intensity images and building geometry. This paper aims at analyzing those pixels contaminated by the multipath propagation and distinguishing different bounce level. Both SAR image simulation and signal statistic analysis are employed
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